In recent years, products conformed with a standard for easily connecting various external devices to a personal computer by wire, for example, the USB (Universal Serial Bus) standard, the IEEE1394 (IEEE (Institute of Electrical and Electronics Engineers) 1394-1995 standard for High Performance Serial Bus) standard are widely generalized. In particular, products conformed with the IEEE1394 standard are generalized as the standard suitable for connecting sound/video devices or a sound/video device and a personal computer by wire. The operation of information reproduction, information recording, or the like in an apparatus to be controlled such as the sound/video device can be also controlled remotely using a control apparatus such as a personal computer connected according to the IEEE1394 standard. As an association for establishing and spreading a common standard to be adhered in the control operation, so-called 1394TA (1394 Trade Association, http://www.1394ta.org/) is established.
An AV/C (Audio Visual/Control) command is used as a control information (command) transmitted/received between the apparatus to be controlled and the control apparatus at the time of controlling the operation of the apparatus to be controlled by the control apparatus. The specification of the AV/C command is standardized by the 1394TA. More concretely, as one of standards determining the specifications of the AV/C command, “TA Document 2001012, AV/C Digital Interface Command Set General Specification Version 4.1” has been announced by the 1394TA. As a part related to the present invention in the standard, in section 11.4, a reserve command is defined as a command for exclusively controlling an apparatus to be controlled only by one control apparatus while excluding the other control apparatuses. According to the standard, specifically, when an apparatus to be controlled to which the reserve command can be applied receives the reserve command from a control apparatus connected to a network conformed with IEEE1394, the apparatus to be controlled recognizes apparatus identification information (generally called GUID (Global Unique ID) which is identification information unique to the control apparatus all over the world) of a control apparatus which outputted the reserve command and, after that, performs an operation written in a control command from the control apparatus whose apparatus identification information was recognized preferentially over operations written in control commands from other control apparatuses.
One of the conventional techniques related to control of an apparatus to be controlled using the reserve command (hereinafter, called a first conventional technique) is an exclusive control method disclosed in Japanese Unexamined Patent Application Publication No. 2001-53766.
There is also HAVi (Home Audio Video interoperability, http://www.havi.org/) as a group for promoting interoperability and standardization of connection of a plurality of information processors using networks including the IEEE1394 standard.
One of the specifications standardized by HAVi is a HAVi specification (full name is “HAVi specification Version 1.1”). In section 3.5 (device control) of the specification, the concept of “DCM (Device Control Modules)” is written as a method of controlling the operation of an apparatus to be controlled from a control apparatus in the network. In section 3.8 (resource manager), a mechanism for exclusively controlling an apparatus to be controlled in the HAVi specification is written.
Specifically, the DCM is a software module as the concept unique to HAVi defining API (Application Program Interface), in which apparatuses to be controlled which are connected to a network are abstracted and operations of them are controlled by a control apparatus in a remote place. In the DCM, as API for exclusively controlling an apparatus to be controlled, the concepts of “reserve (reserve of a control right indicative of exclusive control on the apparatus to be controlled)” and “release (release of the control right)” are defined. The DCM is provided only for a single control apparatus selected from control apparatuses existing on a serial bus conformed with the 1394 standard same as that of the apparatus to be controlled.
The concept of the DCM also permits the case where exclusive control information (to be specific, exclusive control information showing correspondence between an apparatus to be controlled and a control apparatus exclusively controlling the apparatus to be controlled) is stored in an apparatus to be controlled. However, when the apparatus to be controlled itself is an apparatus which is not adapted to an operation based on the exclusive control information, the corresponding exclusive control information is stored in the control apparatus.
In the HAVi specification, only the concepts of “reserve” and “release” are defined as API in the DCM concept for exclusive control between a plurality of control apparatuses. A mode of realizing the API itself in each of the control apparatus and the apparatus to be controlled is not clearly specified. The conventional technique of the exclusive control method conformed with the HAVi specification will be called a second conventional technique hereinafter.
Japanese Unexamined Patent Application Publication No. 2003-116181 discloses another conventional technique (hereinafter, called a third conventional technique) of controlling the operation of an apparatus to be controlled from a remote control apparatus connected to a network to which the apparatus to be controlled is also connected.
In the third conventional technique, a single control server existing in the network has the control rights to control the operations of all of apparatuses to be controlled which are connected in the network. Each of the control rights corresponding to each of the apparatuses to be controlled is given to a control request terminal or the like other than the control server. When a plurality of control apparatuses capable of functioning as control servers exist in the same network, first, a process of acquiring the control right is performed among the control apparatuses, thereby setting a single control server in the network. That is, in the third conventional technique, the control rights on all of the apparatuses to be controlled are collectively controlled by a single control server existing in the network.